Process for polymerizing chlorotrifluoroethylene with bis-heptafluorobutyryl peroxide



Jan. 25, 1955 YQUNG ETAL 2,700,662

PROCESS FOR'POLYMERIZING CHLOROTRIFLUOROETHYLENE WITHBIS-HEPTAFLUOROBUTYRYL PEROXIDE Filed May 17, 1951 POLYMERIZATION OFCHLCROTR'IFLUOROETHYLENE 3 -1' IBIS(HEPTAFLUOROBUTYRYLDPEROXIDE.

----2---- BISCHENDECAFLUOROCAPROYL) PEROXIDE --3-BISCPENTAFLUOROPROPIONYL.) PEROXIDE.

--4-- BISCTRIFLUOROACETYL)PEROXIDE. ----5----'B!S(MONOCHL.OROACETYL.)PEROXIDE R 6 BlSDICHLOROACETYL) PEROMDE. I coMpmsou 1 1--, BlS TmcHLoRpAcamPparaompe I -20 1o b +10 -+2'o +50 +40POLYMERIZATION TEMPERATURE,C.

- INVENTORS DONALD M. YOUNG BRUCE THOMPSON ATTORNEY United. StatesPatent Donald M. Young and Bruce Thompson, Charleston,

W. Va., assignors to Union Carbide and Carbon Corporation, a corporationof New York Application May 17, 1951, Serial No. 226,928 1 Claim. (Cl.26092.1)

This invention relates to the polymerization of halogensubstitutedethylenes; and more especially it relates to a novel process forpolymerizing such compounds in the presence as catalyst of small amountsof certain novel bis(perfluoroacyl) peroxides. The invention hasespecial utility for the polymerization of completelyhalogen-substituted ethylenes free from hydrogen atoms, and containingat least two difierent halogen atoms, including at least one fluorineatom, such as chlorotrifluoroethylene, trichlorofluoroethylene,1,1-dichloro-2,2-difluoroethylene, and mixtures of suchhalogen-substituted ethylenes. However, the invention also is useful forthe polymerization of other halogen-substituted 'ethylenes, such asvinyl chloride, vinyl fluoride, vinylidene chloride, vinylidenefluoride, mixtures of two or more of such monomers, and mixtures ofhalogen-substituted ethylenes with other monomeric polymerizablecompounds containing an ethylenic double bond, such as vinyl acetate,and the lower alkyl esters of acrylic and alpha-methacrylic acids.

Among the more important objects of the invention are the following: toprovide an improved process for making polymers of halogen-substitutedethylenes containing at least one fluorine substituent and one halogensubstituent other than fluorine, and having no hydrogen atoms; toprovide for the production of high molecular weight polymers andcopolymers of such halogen-substituted ethylenes; to provide for theproduction at'good polymerization rates of high molecular weightpolymers of chlorotrifluoroethylene which are more resistant to thermaldecomposition than those heretofore made. These and other objects willbe evident from the following description of the invention.

Resinous polymers of chlorotrifluoroethylene as ordinarily prepared tendto be unstable'and to discolor and undergo severe molecular weightdegradation at temperatures required for the extrusion and -for theinjec-- tion molding of these resins. It has been discovered thatthecontamination of these resins with even. traces of hydrocarbons andvarious other organic compounds containing one or more hydrogen atomsseriously degrades the resins. Moreover, the presence in thechlororecited herein are measured at 230 2,700,662 Patented Jan. 25,1955 ice This invention is based in important part upon the discoverythat a novel class of bis(perfluoroacyl) peroxides, which aresubstantially free from chemically bound hydrogen atoms, are highlyeffective catalysts for the polymerization of chlorotrifluoroethylene.Moreover, the resins produced by the use of these new catalysts are moreresistant to thermal degradation than are those made with the use ofprior known catalysts. When using certain of the new compounds ormixtures thereof as catalysts, it is now possible to conduct thepolymerization of chlorotrifluoroethylene, and mixtures thereof withanother completely halogen-substituted ethylene containing both chlorineand fluorine, at temperatures as high as 12 C. to C. without producingpolymers having unduly low molecular weights.

catalyst for the polymerization of chlorotrifluoroethylene.

By the use of this catalyst, resins resistant to thermal degradation andhaving high molecular weights can be produced at a better combination ofhigh polymerizationtemperature and high polymerization rate than whenusing' other bis(perfiuoroacyl) peroxides.

At present it is not possible to measure directly the molecular weightof polychlorotrifluoroethylene resins, but it has been proved that themolecular weight and melt viscosity of such a resin are related. Themelt viscosities C. on a parallel plate plastometer by the processdescribed by G. J. Dienes and H. F. Klemm in the Journal of AppliedPhysics, vol. 17, pages 458-471 (June 1946). Herein the melt viscosityof a resin is employed as a measure of molecular weight on a relativebasis, and the change in melt viscosity of a resin as a result of itsexposure to elevated temperatures is taken as a measure of molecularweight degradation of the resin. In the case ofpolychlorotrifluoroethylene, those polymers having melt viscosities at230 C. of less than around 0.5 megapoise are brittle and have limitedutility for those applications requiring the use of the poly: mer in thesolid state at normal room temperatures, while polymers having meltviscosities in. excess of,l00 megapoises are more difiicult to fabricateinto useful articles. However, low molecular weight liquid polymers areuseful in lubricating compositions as replacements for hydrocarbonlubricating oils, and are highly resistant to oxidation.

The polymerization of the chlorotrifluoroethylene or otherhalogen-substituted etnylenes preferably is conducted at temperaturesbetween 0 C. and around 50 C.,

trifluoroethylene undergoing polymerization of an alkanol such asmethanol or isopropanol, a dialkyl ether such asdimethyl or diethylether, or ahalogenated ethylene hav- 7 ing a carbon to hydrogen bondgreatly lowers the poly-' and seriously limits the molecular weight Imerization rate, ofthe polymers produced, even when present in amountsaround 0.05% of the .monomer. However, completely fluorinated saturatedaliphatic hydrocarbons have little or no deleterious effects upon thestability of these resins against discoloration and loss of molecularweight at high temperatures. Certain alkanes completely halogenated withfluorine and chlorine can be tolerated in the polybut higher and lowertemperatures can be used less effectively. Autogenous superatmosphericpressures and higher pressures are useful. In such polymerizationsbetween around 0.01% and 0.2% or more of the catalyst commonly is used,being added to the monomer in the form of a dilute solution of theperoxide, containing around. 1 to 10 grams of the peroxide per 100 cc.of solvent, in-a solvent substantially without eflect on thepolymerization, e. g., a saturated organic solvent completelyhalogenated with fluorine or with fluorine and chlorine, preferably acompletely halogenated alkane containing one or more fluorine atomsattached to each carbon atom, with or'without one or more atoms ofchlorine. Examples are trichlorofiuoromethane, dichlorodifluoromethane,

' fluoropentane and merization mixture in amounts up to about l0%without appreciable effect.

Heretofore, such polymers of chlorotrifluoroethylene I have been madeusing as polymerization catalysts dialkyl peroxides such asdi-tertiary-butyl peroxide, alkyl hydro-' peroxides such astertiary-butyl 'hydroperoxide, and esters of-peracids such astertiary-butyl perbenzoate. Diacyl peroxides such as diacetyl. peroxide,dibenzoyl .peroxide and dicaprylyl peroxide have been tried. All ofthese compounds contain carbon to hydrogen bonds. In suchpolymerizations, even if every effort is made throughout thepolymerization and recovery steps to avoid contamination of the resin,the resultant polymer still will be contaminated with residues from thedecomposition of such polymerization catalysts.

'of the relative stability against perfluorooctane.Perfluorotetrahydrofuran can be used. The polymerization can be eliectedin an atmosphere of an inert gas such as nitrogen, although .this is notnecessary.

The polymerization data in Table I oiier a comparison degradation byheat of polychlorotrifluoroethylene resins made using certain of thenovel catalysts of this invention and those resins madeusing certainother types of catalysts, e. g., di-

. acetylperoxide and bis(trichloroacetyl) peroxide. Melt viscositymeasurements were made on various samples of the resins before and aftersubjecting them to a temperature of 300 C. for one hour. The percentageof the initial melt viscosity retained by the samples after the exposureat 300 C. is a measure of the thermal stability of the resin.

In making the resins there were introduced into a glass tube 50 grams ofpurified chlorotrifiuoroethylene and the indicated per cent of thecatalyst, basedupon the weight of the monomer. The monomer used inpreparing the resins had been purified by careful recti- Of importancein the evaluation of a polymerization catalystare the rate of'polymerization obtainable at a given temperature, and the molecularweight of the resultant polymer. In general, for a given catalyst,

fication inan efficient tractionating column. In: the the greater thecatalyst concentration, the greater is the runs using thebis(perfiuoroacyl)- peroxides and bis(-trirate. of polymerization, andthe lower 18. the molecular chloroacetyl) peroxide, the catalyst wasintroduced as aweight of. the polymer formed; while higherpolymerizasolution containing approximately 2.5 grams of the tiontemperatures yield higher polymerization rates and peroxide per 100 cc.of a 50150-by volume mixture ofdecreased molecular weight polymers.Practical limitatrichlorofluoromethane and l,l,2-trichloro-l,2,2-tr1- 1tions, however, impose rather rigid restraints upon the fiuoroethane. Inthe case of the run using diacetyl degree. tOWhlCll. catalyst.concentrations and polymerizaperoxide, the latter was used in the formof a 20% solution temperatures can be adjusted in seeking favorable tionin dimethyl phthalate. The tube then was flushed polymerization ratesforthe production of resins having with nitrogen, sealed, andimmersed ina water bath a range of molecular weights satisfactorily higlr, e. g.,at the indicatedpolymerization temperature fora sufthose corresponding.to melt. viscosities of around 0.5 ficient time to give about a- 10%conversionto-polymer; megapoise or more. The tubes: thenwere removed,chill'ed in Dry Ice and Table-.II: presents data illustrating theeftects 'of varyopened. After most. of the residual monomer had ing thexpolymerizationa temperatures upon the rate of: weathered oft, thepolymer was. dried at 60 C. overpolymerization ofchlorotrifiuoroethylene and upon the night, and then at 200 C. forfivehours. After demelt viscosity at 230 C of the resultant polymer. Intermining the initial melt viscosity of the resin, it was each-.run,0.025%: by weight of the' catalyst, based'upon heatedxto-300 C. for onehour with dry heat, and then the monomer,. was used; Thepolymerizatioris were the melt viscosity was again determined. It willbe limite'd;to low-conversionsof' monomer in. order tomininoted' thatthe resinsmade with the catalysts: of this. mize variations. inmolecular weight. arising from difmventioni were much more resistant tothe action of the. ferences in: the. degree. of conversion. The.polymerizaheat than were the other resins. tions, the: data of whichappear. in T ableII, were con ducted. under the same general conditionsused in the.

TABLE, I polymerizations upon which Table I isbased; and the polymerwas: recoverediin' the same manner. Melt viscosity; The accompanyingdrawing presents in. graphic form Mega-B91505 at portions of: the dataof Table II. In the drawing the Catalyst Puma" Melt product of thepolymerization rate, in terms of weight 0 Concenzatlon Viscosity,

aly nation, Tempm. Retained; per cent of monomerpolymei'ized per hour,and the melt Percent ture,0. mt ififter 1; Percent viscosities at 230 C.of. the polymer formed, in terms: 65?; of megapoises, has been plottedagainst the polymerization temperature for each run. It is apparent fromthe drawing that a more favorable polymerization rateand: Bis(heptafluorohutyryl) per0x1d9 (r 25 3 7, 6g molecular weightrelationship for a given polymerization: Bis (g ifluora-aaetyl) 0o 5 v 45 9 h temperature is securable with the bis(perfluoroacyl) gf z g g g zy 2 0 a peroxides of this invention than with the chloroacetyl' peroxld0:0 0' 6.6 2.2" 33 peroxides-examined- Th1s is-especially trueofbis(hepta- Y1'petoxide.- 0:10 25 8-2 .0 fluorobutyryl) peroxide;although bis(trifluoroa'cetyl)" peroxide offers advantages on the basisof its lower-cost Norm- 'For comparison. Of production:

TABLE II mymmam" Melt Vis- Polymer-i Catalyst i isi ii t gt e e aairF535, Tlme gig Percent potse s'zat Melt.V1s- L n f Hours Hr; 230C.coslty B1s(trifluoroacetyl)-peroxi 9-. 25.: 49. 0.15 7:5 39 a 37.5 66.0111 i 7.4- 15. i 21 B ls(pe tafluoropropionyl)'peroxide.-... 12:5" 0.291426 150 43' Do-. 5 25 16a 0. 56" 9.0 115. a: Bis(heptafluorohutyryl); I

peroxide 12. a" 40: 0.35- 13:9 220. 77.- D 25- 1a 0.81 13.0 26 21* Do351 18. 5 0. 49 9. 0 6 3' Bishendeeatluor 1 caproyllperoxldee. m5 215.0:50 12.4 82 41: 0; i 25- 16 0.66 10.6- 14 9 Bis(monoehloroaeety1);

peroxide; 25 110 0.09. 9.9 5

0v 33.5. 0.22 7.4 150 as 12. 5. 16 0.68 10.9. 27 1a 25 8 089 7.1 4 4Norm-'Foreomparison'.

Copolymerization f chlorotrifluoroethylene and trichlorofluoroethylene Achilled pressure tight container was charged with 45 grams ofchlorotrifluoroethylene, grams of trichlorofiuoroethylene, and 0.05 gramof bis(heptafluorobutyryl) peroxide, the latter being introduced in theform of a solution containing 2.5 grams of the peroxide per 100 cc. of amixture of equal volumes of 1,1,2-trichloro-1,2,2-trifiuoroethane andtrichlorofluoromethane. The container was flushed with nitrogen, sealed,and held at 25 C. in a water bath for 17 hours. The resultant resinouscopolyrner contained around 65% of the chlorotrifluoroethylene in thepolymer.

Copolymerizaltion of chlorotrifluoroethylene and 1,1 -dichl0ro-2,2-difluoroethylene Production of polyvinyl chloride A chilled glasscontainer was charged with 25 grams of liquid vinyl chloride and 0.025gram of bis(heptafluorobutyryl) peroxide (the latter being added as asolution containing 2.5 grams of the peroxide per 100 cc. of a mixtureof equal volumes of 1,1,2-trichloro- 1,2,2-trifluoroethane andtrichlorofiuoromethane). The container was flushed with nitrogen,sealed, and placed in a water bath held at 25 C. After two hours thecontainer was chilled in Dry Ice, opened, and the polymer was driedovernight at 60 C. and weighed. A conversion of 20.8% of the monomer toa polyvinyl chloride having a reduced viscosity in cyclohexanone of 1.8was secured, at an average conversion rate of 10.4% of the monomer perhour.

Production of polyvinylidene chloride Following the general proceduredescribed herein for the production of polyvinyl chloride, a mixture of40 grams of vinylidene chloride and 0.040 gram of bis-(heptafluorobutyryl) peroxide gave, after 1.75 hours of polymerizationat 25 C., an 8.0% conversion of the monomer to polyvinylidene chloride,at an average conversion rate of 4.6% of the monomer per hour.

. The bis(perfiuoroacyl) peroxides used as polymerization catalysts inthe process of the invention have structures corresponding to theformula:

wherein n designates an integer of from 1 to 10 and CnF(2n+1) can be aprimary, secondary or tertiary fluorine-substituted alkyl group. Theycan be made by vigorously agitating an aqueous solution of an alkalimetal peroxide at temperatures within the range between around 15 C. and25 C. with an acyl halide of a perfluoro fatty acid, such astrifluoroacetyl chloride, dissolved in a mixture of equal volumes of1,1,2-trichloro-l,2,2-trifluoroethane and trichlorofluoromethane, thealkali metal peroxide and perfluoroacyl halide being in the molar ratioof 1 to around 1.5 or more, and the said solution of the halide beingfed rapidly to the aqueous solution of the alkali metal peroxide. Thereaction mixture is allowed to stratify, and the solvent layer whichcontains the bis(perfiuoroacyl) peroxide, is separated and stored at lowtemperatures, preferably around 15 C. or lower. The solution can be useddirectly without purification in the polymerization, diluted with thesaid solvent if necessary to provide a solution having from 1% to 10% byweight of the solute.

By the practice of this invention, it is possible to polymerizecompletely halogen-substituted ethylenes such aschlorotrifiuoroethylene, and to secure thereby resins having averagemolecular weights sufliciently high to adapt the resins for commercialuses, and which resins are more resistant to thermal degradation thanresins made using catalysts heretofore known, and to effect this resultusing higher polymerization temperatures and polymerization rates thanhas been possible heretofore.

The invention is susceptible of modification within the scope of theappended claim.

We claim:

Process for making polymers of chlorotrifluoroethylene, which comprisescontacting chlorotrifluoroethylene at a temperature within the rangefrom around 0 C. to around 50 C. with a small amount of his-(heptafiuorobutyryl) peroxide.

References Cited in the file of this patent UNITED STATES PATENTS2,531,134 Kropa Nov. 21, 1950 2,559,630 Bullitt July 10, 1951 2,564,024Miller Aug. 14, 1951 2,586,550 Miller Feb. 19, 1952

